Microtiter plates (sometimes referred to as “microplates”) are plates with multiple individual wells that are commonly used as small test tubes during the experimental process. Microtiter plates typically have 6, 24, 96, 384, or even 1536 sample wells arranged in a 2×3 rectangular matrix. Each well of a microtiter plate typically holds somewhere between a few to a few hundred microliters of liquid.
Robotic mechanisms are often used in the laboratory to transport microtiter plates from one location to another during an experimental assay. For example, a robotic mechanism may be used to transport a microtiter plate from a first station where liquids are dispensed into the wells of the microtiter plate to a second station where the contents of the wells are tested for various characteristics.
Laboratory microtiter plates and the automated laboratory instruments used to handle such microtiter plates are commonly viewed as essential tools in drug discovery research. Because of the need for interaction between microtiter plates and various automated laboratory instruments, dimensional standards have been established for microtiter plates. The makers of automated laboratory instruments have come to rely on these dimensional standards for their products that handle microtiter plates.
The most widely accepted dimensional standards for laboratory microtiter plates have been established by the American National Standards Institute (ANSI) in cooperation with the Society for Biomolecular Screening (SBS). These standards are set forth in ANSI publications ANSI/SBS 1-2004 through ANSI/SBS4-2004. As used herein, the term “standard microtiter plate” is intended to refer to a microtiter plate substantially conforming to these ANSI dimensional standards.
A standard microtiter plate according to ANSI/SBS 1-2004 is shown in FIG. 1. The microtiter plate 20 includes ninety-six wells 21 formed in a rectangular 2×3 matrix. The microtiter plate of FIG. 1 is shown in a landscape orientation with 12 columns and 8 rows. If the microtiter plate of FIG. 1 is rotated 90°, it will be in a portrait orientation with 8 columns and 12 rows of wells. The microtiter plate includes two opposing longer sides 22, 24, with each longer side about 5″ in length. The microtiter plate also includes two opposing shorter sides 26, 28, with each shorter side about 3⅜″ in length.
During a particular experimental assay, a microtiter plate may need to be oriented in various directions at various times to accommodate various instruments. For example, consider an experimental process where a clean microtiter plate is initially oriented in landscape fashion on a platform. The microtiter plate is then moved to a first instrument where it must be loaded in a portrait orientation. After the microtiter plate is processed by the first instrument, it must be moved to a second instrument which requires loading in a landscape orientation. Following processing by the second instrument, the microtiter plate is unloaded to a cleaning station that requires a portrait orientation. Accordingly, it can be seen that various orientation changes in the microtiter plate may be necessary during a given experimental assay.
Various automated laboratory instruments are available to transport microtiter plates between different locations and different orientations. A common laboratory instrument used to transport microtiter plates is the Cartesian coordinate robot. Cartesian coordinate robots have at least two principal axes of control that are linear and are at right angles to each other. Thus, a Cartesian coordinate robot may include a robotic hand operable to move along a vertical path of travel or a horizontal path of travel. One common type of Cartesian coordinate robot available for transporting microplates is the Gantry robot. Gantry robots generally include a horizontal member supported at a central location or at opposite ends. A carriage is configured to travel upon the horizontal member in a horizontal direction of travel. The carriage is also configured to support a robotic arm configured to move in a vertical direction of travel with respect to the carriage.
Cartesian coordinate robots used to transport microtiter plates are often equipped with opposing grip members configured to rotate with respect to the robotic arm. The opposing grip members are designed to move toward and away from each other by a given stroke distance. When the grip members in a far apart position, they can be moved to the sides of the microtiter plate. When the grip members are then moved to a closer position, the surfaces of the grip members contact opposing sides of the microtiter plate. As the grip members contact the sides of the microtiter plate, a force is applied to the sides of the microtiter plate, and the grip members may be used to pick up and move the microtiter plate from one place to another. Also, the grip members may be rotated with respect to the robotic arm to change the orientation of the microtiter plate from a landscape orientation to a portrait orientation, or vice-versa.
Even though the grip members on the Cartesian coordinate robots described above may be rotated, the robots occasionally encounter problems grasping a microtiter plate. In one situation, a platform holding a microtiter plate may only expose two of the four sides of the microtiter plate to the grip members of the robot. For example, a particular loading platform may expose the shorter sides of the microtiter plate, but may include a wall around the longer sides of the microtiter plate. Such a wall around the longer sides of the microtiter plate will prevent the robot from grasping the microtiter plate if the grip members are designed to grasp the longer sides of the microtiter plate rather than the short sides. Accordingly, it would be advantageous to provide a laboratory robot having opposing grip members operable to move over a sufficient stroke distance in order to allow the grip members to contact either the longer sides or the shorter sides of a standard microtiter plate.
Another situation where laboratory robots sometimes encounter problems in grasping microtiter plates is when there is a significant amount of equipment next to the loading platform. In these situations, the arrangement of the robot and the instruments surrounding the loading platform may prevent the robot from approaching the platform from various horizontal directions. Thus, it would be advantageous to provide a laboratory robot capable of approaching a microtiter plate from a vertical direction. It would be of further advantage if the vertical approach of the robot could occur within a relatively narrow cylindrical column directly above the microtiter plate. In addition, it would be advantageous if such robot comprised opposing grip members configured to rotate about an axis within such relatively narrow cylindrical column.